Getting more that 1Vrms out of my sound card

[windchimes]

Hello all! New user, first thread, and I apologize if this has been answered elsewhere but I can't find it!

Update: Major edit based on additional research and testing.

I am using REW with a Focusrite Scarlett Solo Gen 3, for distortion analysis of high-impedance circuits. The Scarlett is spec'd to output up to +15.5 dBu, which would be 4.6Vrms into a balanced load, or 2.3Vrms single-ended. I used Audacity to generate a 0 dBFS sine wave, which got the Scarlett to output 2.4Vrms single-ended, with the output volume at max. This actually slightly exceeds Focusrite's spec (I would expect +9.5 dBu single-ended, which is 2.3Vrms).

However, if I use the Generator in REW (also set to 0dBFS), I only get 1.2Vrms single-ended - 6dB down. It's like the MSB isn't turning on somehow.

I have the interface set to 48kHz, and according to the main screen in REW (and AudioMidi Setup - I'm on a Mac) the bit depth is 24. Same settings in Audacity.

As an additional test, I used both REW and Audacity to generate .wav files of sine tones at 0dBFS, and compared the signal maxes and mins by reading the arrays into a Jupyter notebook in Python, for both 24 bit PCM and 32 bit float encoding. The peak maximums are the same. Audacity's peak minimums are a bit lower but the difference is on the order of 10^-7.

Any help troubleshooting this would be greatly appreciated! I could really use the extra voltage! Thank you

 

[John Mulcahy]

if I use the Generator in REW (also set to 0dBFS), I only get 1.2Vrms single-ended

With what driver selection? If you are using ASIO you should get the same result, with Java drivers the Windows volume control may be in the path. For Java choose device names starting with EXCL to use WASAPI Exclusive drivers.

 

[windchimes]

Hi John, thanks for REW, and thanks for your reply!

I am on a Mac (14.6.1). I believe everything goes through CoreAudio? I don't seem to have a lot of controls/options.

Here are the relevant preference screens. I didn't include the System Settings/Sound one - if I select the Scarlett for either input or output, the system volume level fader is grayed out.

I did another experiment where I calibrated the Scope in REW, then set the Scarlett as input to REW and output of Audacity, and verified my previous result with the REW Scope.

Please let me know if there is any other troubleshooting to try. Thank you!